Objective: To explore cell death and apoptosis in rat hippocampal neurons at different time points after ischemia, hypoxia and reperfusion injury and to elucidate time window characteristics in ischemia neuronal injury.Methods: Hippocampal neurons were obtained from rat embryo and were cultured in vitro. The ischemia and reperfusion of cultured rat hippocampal neurons were simulated by oxygen-glucose deprivation (OGD) and recovery. OGD at different time points (0.25 h to 3.0 h) and then the same recovery (24 h) were prepared. Annexin V-PI staining and flow cytometry examined neuron death and apoptosis at different time after injury. Results: After OGD and recovery, both necrosis and apoptosis were observed. At different times after OGD, there were statistically significant differences in neuron necrosis rate (P<0.05), but not in apoptosis rate (P>0.05). At recovery, survival rate of hippocampal neurons further decreased while apoptosis rate increased. Furthermore, apoptosis rates of different time differed greatly (P<0.05). Apoptosis rate gradually increased with significant difference among those of different time points (P<0.05). However, 2 h after ischemia, apoptosis rate decreased markedly.Conclusions: Apoptosis is an important pathway of delayed neuron death. The therapeutic time window should be within 2 h after cerebral ischemia and hypoxia.